Multiplexing of data is used in an increasing number of commercial trucks, agricultural vehicles, off-road equipment and marine applications. Controller Area Network buses known as "CAN-buses" (such as SAE J-1939) are being adopted in many future commercial vehicle programs and in industrial applications (such as DeviceNet.) A detailed description of multiplexing can be found in the SAE (Society of Automotive Engineers) Technical Series paper entitled "Practical Perspectives on Physical Layers for Truck Multiplexing," which is fully incorporated herein by reference.
The CAN-bus physically is a cable, as shown FIG. 1. It was first developed by Bosch and used in Mercedes-Benz S-series cars. Many semiconductor makers (including Intel, Motorola, Siemens, Philips, NEC, national Semiconductor) have produced CAN chips and microprocessors with CAN functions. The cable for the CAN-bus contains two signal wires and a drain wire. The signal wires are termed CAN-H and CAN-L. The drain wire is termed CAN-SHLD. The drain wire allows easy termination of the shield to drain away stray current caused by electromagnetic radiation.
There are two ways to make connections from the CAN-bus to ECUs (Electronic Control Units). One way is shown on the right side, below ECU n+1 in FIG. 1, wherein several connectors are used. The connector labeled A-B-B is a T-connector. The other connectors are mating connectors labeled B-mate and A-mate. A T-connection method is one way for a stub (i.e. branch) to be connected to the CAN network. The T-connection system includes a T-connector and three mating connectors. When needed, a heat shrinkable tube is used to seal the ends of the connectors from the external environment.
One alternative to the T-connection system employs ultrasonic welders to respectively weld CAN-H, CAN-L and CAN-SHLD wires. Ultra-sonic welding is a type of friction welding that joins the copper wires by vibrating them in shear while clamping the wires together. The vibration causes the copper molecules to mingle and diffuse, forming a true metallurgical bond. Only un-tinned wires are used in this process. The welded CAN-H, CAN-L and CAN-SHLD splices are separated with insulators. A covering, including a foil shield and protective vinyl tape, is then applied over the entire splice assembly. The splice assembly is then covered with shrinkable tubing to protect against environmental factors. The finished package is small and allows easy routing through tight spaces. The splices are protected from moisture and other contaminants. A splice connection (SC) and a T-connector (TC) are illustrated in FIG. 2.
In SAE J-1939, which is a recommended practice of the Society of Automotive Engineers (SAE), a T-connector is recommended as a method to connect a device to the CAN-network using a jacketed cable of a twisted pair, a drain wire and continuous conductive foil. However, the T-connector is expensive to manufacture. The splicing method was also adopted as a recommended practice to commercial trucks, with a lower overall cost than the T-connector. However, there remains some difficulties in processing splices. Accordingly, the cable jacket has been modified to make it easier to strip, and the wire has been modified to be non-tinned to allow use of ultrasonic welding. Moreover, several heat-shrink methods are being investigated for potential cost reductions and quality improvement.
There is another recommended practice, i.e. J1939-15 or "Lite." The "Lite" cable consists of the jacketed unshielded twisted pair only. There is no drain wire and shield. This opens up possibilities of using new connectors for the "lite."
The present invention is directed to a device and method for a reliable, inexpensive, easy-to-assemble, serviceable, compact databus multiplexing connection system for connecting electronic control units (ECUs) to a databus, such as the CAN-bus.